This adventure described the first place where the TARDIS materialised after the television story The Sensorites, at the end of which the First Doctor had promised to throw Ian and Barbara out. Ironically, at the end of this adventure, the Doctor returned to his idea of throwing them out, thus leading directly into the events of the television story The Reign of Terror.

The story has the prerequisites to be considered a historical story: no prominent science fiction elements outside of the TARDIS and the main characters. However the conflict in this story is indirectly caused by the telepathic abilities of the Sensorites and the effects they have on the TARDIS crew being carried over from that story to this one.

Several mentions are made of the Sense Sphere and of the telepathic enhancement that Susan experienced there. (TV: The Sensorites) This story takes place immediately after that one, with the Doctor preparing to throw Ian and Barbara out of the TARDIS the next place they land.

Barbara repeats several times "I am your navigator. I will lead you back," which is a close paraphrase of what Ian said about her in TV: The Sensorites. "This is our navigator. She is going to lead us back."